How to upgrade your Mac OS?
Step 1: Go to https://support.apple.com/en-us/HT208969
Step 2: Go to Apple Icon and click on "About this Mac”
Step 3: Find out what is your Mac specs info
Step 4: Check compatibility
Step 5: If your device meets the compatibility, before proceed to upgrade, please BACKUP ALL YOUR FILES.
Step 6: For the strongest security and latest features, find Find out whether you can upgrade to macOS Catalina. If you still need macOS High Sierra, click on the link "Get macOS High Sierra". It will open in the App Store. Download and Install.
Step 7: Proceed to download and install the Proctortrack app.